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- // SPDX-License-Identifier: GPL-2.0-only
- /*
- * umd - User mode driver support
- */
- #include <linux/shmem_fs.h>
- #include <linux/pipe_fs_i.h>
- #include <linux/mount.h>
- #include <linux/fs_struct.h>
- #include <linux/task_work.h>
- #include <linux/usermode_driver.h>
- static struct vfsmount *blob_to_mnt(const void *data, size_t len, const char *name)
- {
- struct file_system_type *type;
- struct vfsmount *mnt;
- struct file *file;
- ssize_t written;
- loff_t pos = 0;
- type = get_fs_type("tmpfs");
- if (!type)
- return ERR_PTR(-ENODEV);
- mnt = kern_mount(type);
- put_filesystem(type);
- if (IS_ERR(mnt))
- return mnt;
- file = file_open_root_mnt(mnt, name, O_CREAT | O_WRONLY, 0700);
- if (IS_ERR(file)) {
- kern_unmount(mnt);
- return ERR_CAST(file);
- }
- written = kernel_write(file, data, len, &pos);
- if (written != len) {
- int err = written;
- if (err >= 0)
- err = -ENOMEM;
- filp_close(file, NULL);
- kern_unmount(mnt);
- return ERR_PTR(err);
- }
- fput(file);
- /* Flush delayed fput so exec can open the file read-only */
- flush_delayed_fput();
- task_work_run();
- return mnt;
- }
- /**
- * umd_load_blob - Remember a blob of bytes for fork_usermode_driver
- * @info: information about usermode driver
- * @data: a blob of bytes that can be executed as a file
- * @len: The lentgh of the blob
- *
- */
- int umd_load_blob(struct umd_info *info, const void *data, size_t len)
- {
- struct vfsmount *mnt;
- if (WARN_ON_ONCE(info->wd.dentry || info->wd.mnt))
- return -EBUSY;
- mnt = blob_to_mnt(data, len, info->driver_name);
- if (IS_ERR(mnt))
- return PTR_ERR(mnt);
- info->wd.mnt = mnt;
- info->wd.dentry = mnt->mnt_root;
- return 0;
- }
- EXPORT_SYMBOL_GPL(umd_load_blob);
- /**
- * umd_unload_blob - Disassociate @info from a previously loaded blob
- * @info: information about usermode driver
- *
- */
- int umd_unload_blob(struct umd_info *info)
- {
- if (WARN_ON_ONCE(!info->wd.mnt ||
- !info->wd.dentry ||
- info->wd.mnt->mnt_root != info->wd.dentry))
- return -EINVAL;
- kern_unmount(info->wd.mnt);
- info->wd.mnt = NULL;
- info->wd.dentry = NULL;
- return 0;
- }
- EXPORT_SYMBOL_GPL(umd_unload_blob);
- static int umd_setup(struct subprocess_info *info, struct cred *new)
- {
- struct umd_info *umd_info = info->data;
- struct file *from_umh[2];
- struct file *to_umh[2];
- int err;
- /* create pipe to send data to umh */
- err = create_pipe_files(to_umh, 0);
- if (err)
- return err;
- err = replace_fd(0, to_umh[0], 0);
- fput(to_umh[0]);
- if (err < 0) {
- fput(to_umh[1]);
- return err;
- }
- /* create pipe to receive data from umh */
- err = create_pipe_files(from_umh, 0);
- if (err) {
- fput(to_umh[1]);
- replace_fd(0, NULL, 0);
- return err;
- }
- err = replace_fd(1, from_umh[1], 0);
- fput(from_umh[1]);
- if (err < 0) {
- fput(to_umh[1]);
- replace_fd(0, NULL, 0);
- fput(from_umh[0]);
- return err;
- }
- set_fs_pwd(current->fs, &umd_info->wd);
- umd_info->pipe_to_umh = to_umh[1];
- umd_info->pipe_from_umh = from_umh[0];
- umd_info->tgid = get_pid(task_tgid(current));
- return 0;
- }
- static void umd_cleanup(struct subprocess_info *info)
- {
- struct umd_info *umd_info = info->data;
- /* cleanup if umh_setup() was successful but exec failed */
- if (info->retval)
- umd_cleanup_helper(umd_info);
- }
- /**
- * umd_cleanup_helper - release the resources which were allocated in umd_setup
- * @info: information about usermode driver
- */
- void umd_cleanup_helper(struct umd_info *info)
- {
- fput(info->pipe_to_umh);
- fput(info->pipe_from_umh);
- put_pid(info->tgid);
- info->tgid = NULL;
- }
- EXPORT_SYMBOL_GPL(umd_cleanup_helper);
- /**
- * fork_usermode_driver - fork a usermode driver
- * @info: information about usermode driver (shouldn't be NULL)
- *
- * Returns either negative error or zero which indicates success in
- * executing a usermode driver. In such case 'struct umd_info *info'
- * is populated with two pipes and a tgid of the process. The caller is
- * responsible for health check of the user process, killing it via
- * tgid, and closing the pipes when user process is no longer needed.
- */
- int fork_usermode_driver(struct umd_info *info)
- {
- struct subprocess_info *sub_info;
- const char *argv[] = { info->driver_name, NULL };
- int err;
- if (WARN_ON_ONCE(info->tgid))
- return -EBUSY;
- err = -ENOMEM;
- sub_info = call_usermodehelper_setup(info->driver_name,
- (char **)argv, NULL, GFP_KERNEL,
- umd_setup, umd_cleanup, info);
- if (!sub_info)
- goto out;
- err = call_usermodehelper_exec(sub_info, UMH_WAIT_EXEC);
- out:
- return err;
- }
- EXPORT_SYMBOL_GPL(fork_usermode_driver);
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